1. Technical Field of the Invention
The present invention relates to an ink-jet head control circuit, an ink-jet head module, a data transmission method, and a liquid drop discharge apparatus.
2. Description of the Related Art
An overview of a head unit of an ink-jet liquid drop discharge apparatus and a driving device thereof will be described with reference to FIG. 10.
FIG. 10 schematically shows the structure of a liquid drop discharge apparatus 900 comprising an information processor main body 910 (hereinafter, referred to as a driving device) that is a control subject, and a head unit 950 to be controlled. In FIG. 10, the driving device 910 includes a driving signal generator 915 which generates a driving signal Vout to discharge liquid drops through a plurality of nozzles, and a data storage unit, which converts driving data input from a high-rank unit (not shown) into data having a structure suitable for transmission to the head unit 950 and outputs the converted driving data in series, that is, a latch circuit 911, and a shift register 913. A print timing signal (PTS) for driving is input to the latch circuit 911 from the high-rank unit, and the latch circuit 911 receives driving data input at a rising edge of the print timing signal PTS and stores the input driving data.
A latch signal LAT, which is obtained by delaying the print timing signal PTS for a predetermined amount of time, is supplied to the driving signal generator 915 from the high-rank unit. In addition, a static voltage VH of about 30 V is applied to the driving signal generator 915 and becomes a power source for a driving signal. The driving signal data input from a data bus is digital-to-analog (D/A) converted by the driving signal generator 915 and is output as the driving signal Vout.
Further, as shown in FIG. 10, the head unit 950 includes a shift register 951 for inputting data DATA which is driving information for each nozzle, a latch circuit 952 which stores the data DATA of the shift register 951, a selector 953 which selects driving/non-driving, and a nozzle driving unit 954 which has an actuator for driving a nozzle (not shown) communicating with each of a plurality of liquid drop containers. The shift register 951 converts the data DATA that is input serial data, into parallel data. The latch circuit 952 is a data storage unit that stores the parallel data output from the shift register 951 for each nozzle. In addition, the selector 953 is configured so that the driving signal Vout is transmitted from the driving device 910, driving information distributed for each nozzle is applied to a desired nozzle only during driving and is not applied to the desired nozzle during non-driving. In the nozzle driving unit 954, actuators to which the driving signal Vout is applied are driven and liquid drops are discharged through a plurality of nozzles. A logic power source Vcc and a ground line GND are power source lines. A voltage of +5 V or +3.3 V is supplied to the logic power source Vcc.
An object substrate on which liquid drops are discharged using the aforementioned ink-jet liquid drop discharge apparatus has become larger. As the object substrate becomes larger, a distance that a head unit and a table on which a substrate is installed make a relative motion, that is, a main scanning distance becomes longer. The head unit and the driving device are connected through a flexible flat cable (FFC), for example. As the main scanning distance becomes longer, a signal path, such as an FFC, also becomes longer. If the signal path becomes longer, the ratio of the influence of noise from the outside becomes larger. Due to the influence of noise, the liquid drop discharge apparatus cannot perform a normal discharge operation. Further, for improvement of productivity, the number of head units or the number of nozzles tends to be increased. Thus, the data transmitted to the head unit increases. As such, the power consumption of the driving device or the head unit increases. For example, since the object substrate is large in a liquid drop discharge apparatus for industrial use, the influence of noise and the increase in power consumption cannot be ignored. The influence of noise and the increase in power consumption become larger when the main scanning distance is long and liquid drops are uniformly and consecutively discharged on the object substrate (so-called, the application of liquid drops to the entire surface of a region).
The present invention has been made to address the above problem in the prior art. It is therefore an object of the present invention to provide an ink-jet head control circuit, an ink-jet head module, a data transmission method, and a liquid drop discharge apparatus to reduce the influence of noise and to have low power consumption.